Vulnerability · Published Aug 21, 2026 · Assigned by cisa-cg
CVE-2026-49114ONNX symlink-following and path-traversal arbitrary file write
High 7.1
In plain English
A high-severity path traversal in ONNX from ONNX. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 5% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
In ONNX before 1.21.0, the 'save_external_data' function builds the external-data file path from the model's external_data location field and opens it for writing without 'O_NOFOLLOW/O_EXCL', after a non-atomic 'os.path.isfile()' check. A local attacker with write access to the directory where a victim serializes external data can deterministically pre-plant a symlink that is being followed, causing the victim's write to append to any file the victim can write, e.g. ~/.ssh/authorized_keys, cron files, or application configs. Fixed in 1.21.0.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | onnx | no fix listed | DEBIAN-CVE-2026-49114 |
| Debian:13 | onnx | no fix listed | DEBIAN-CVE-2026-49114 |
| Debian:14 | onnx | no fix listed | DEBIAN-CVE-2026-49114 |
| PyPI | onnx | 1.21.0 | GHSA-q56x-g2fj-4rj6 |
| PyPI | onnx | 1.21.0 | PYSEC-2026-3876 |
| Ubuntu:22.04:LTS | onnx | no fix listed | UBUNTU-CVE-2026-49114 |
| Ubuntu:26.04:LTS | onnx | no fix listed | UBUNTU-CVE-2026-49114 |
| Ubuntu:26.10 | onnx | no fix listed | UBUNTU-CVE-2026-49114 |
Affected products (as reported)
Weakness: CWE-367, CWE-22, CWE-59 · Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H